Influence of reaction conditions on the rate of enzymic polymerization of pyrogallol using laccase

Laccase produced from Trametes versicolor (ATCC 200801) was utilized to synthesize poly(pyrogallol) in aqueous solution. The polymerization reaction was conducted batchwise in a closed, temperature controlled system containing sodium acetate buffer for pH stability. The effects of monomer (pyrogallol), enzyme and dissolved oxygen concentrations, reaction mixture pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen in the reaction mixture. Maximum initial oxygen consumption rates, defined as initial polymerization reaction rate, were achieved with sodium acetate buffer of pH 4.5, temperature at 45 °C and 18 mg/L of dissolved oxygen concentration. Typical saturation enzyme kinetics were observed for enzymic polymerization using 1000 mg/L initial pyrogallol and 216 U/L enzyme. The initial dissolved oxygen consumption rate increased with temperature up to 45 °C, after which the rate decreased due to apparent enzyme denaturation.